Could trees be the chemical recycling centres of the future?

Researchers at the University of British Columbia Okanagan hope to learn whether chemicals absorbed by trees from contaminated soil can be retrieved and re-used

Poplar trees planted on a decommissioned landfill site in Salmon Arm, B.C. act as a living recycling facility, taking up contaminants from the soil and transforming them into usable chemicals. (Photo courtesy David Derbowka, Passive Remediation Systems Ltd.)

Trees are pretty useful to humans: they produce oxygen, provide lumber, and, if a B.C.-based research project is successful, they might help society turn harmful contaminants into useful chemical products like natural fertilizer, insecticides, antibacterials and antioxidants.

UBC Okanagan chemistry professor Susan Murch has partnered with local environmental remediation company Passive Remediation Systems Ltd. (PRS) to study how trees can absorb contaminated soil and change it into something usable.

PRS is using hybrid poplar trees to decontaminate a former landfill site in Salmon Arm, B.C. The hardy trees act as a sort of natural sponge, absorbing pollutants from the soil, and have been used in numerous environmental remediation projects in the B.C. interior since 2004. But how exactly the trees transform these chemicals — and whether the end product can be retrieved in a usable form — is a mystery Murch hopes to solve.

First, PRS harvests leaves and stems from its poplars and cooks them in a sealed oven to produce "biochar," a solid compound which can be used as material for 3D printing or mixed with compost to form a chemical-rich fertilizer. A by-product of the cooking process is "wood vinegar" — a steam extract that Murch and her team will analyse for useful molecules.

"Trees are really interesting chemical factories," she explains. "They can’t run away from threats that happen to be close to them, so their only way to interact with the world is through chemistry."

When faced with adverse soil conditions, trees may sequester harmful chemicals within pockets in their cells, or they might neutralize toxins from their environment using molecules they produce themselves. The way they deal with metals left behind in an oilfield tailings pond might differ from how they deal with trace pharmaceuticals or household cleaning products found at a municipal sewage treatment plant.

"My part in this project is really to understand what useful chemicals are produced by the trees and how we can extract them to make new products," Murch says.